1. Field of the Invention
The present invention relates generally to stretching dough, such as confectionary dough, bread dough, or the like, and particularly, to an apparatus for continuously stretching a strip of dough, fed in various thicknesses, into a thin sheet of dough.
2. Description of Prior Art
U.S. Pat. No. 4,113,819 discloses a stretcher comprising three serially arranged belt conveyors and an endless roller mechanism arranged above the conveyors.
Although the upper flight of the entrance belt conveyor of the stretcher in this prior art is adapted to have an angle against the lower straight portion of the endless roller mechanism, the relationship between the upper flight of the entrance conveyor and the straight portion of the endless roller mechanism is stationary. It is, therefore, impossible to retain a specified area where both the upper flight and the straight portion of the roller mechanism fully contact the dough fed therebetween regardless of the change in the thickness of the dough supplied onto the stretcher.
Australian Patent No. 545,313 discloses a stretcher comprising two serially arranged belt conveyors and an endless roller mechanism.
This stretcher can angularly adjust the upper flight of an entrance belt conveyor in relation to the straight portion of the roller mechanism in response to the change in the dough thickness. Also, the feed speed ratio between the two conveyors can be varied to control the feed speed of the entrance belt conveyor.
Although the stretcher in this prior art performs fairly well, a sufficient stretching effect cannot be obtained when a high ratio of thickness reduction by stretching is required, because stretching is carried out between only two belt conveyors.
In general, when a viscoelastic material, such as bread dough or confectionary dough, which generally has a low resistance against exterior force and whose properties are not uniform, is to be stretched to exact dimensions, gentle stretching by the largest possible number of conveyors gives superior results.
To obtain such superior results, an apparatus with three conveyors has been studied. In such an apparatus, the feed speed of the intermediate conveyor relative to those of the inlet and outlet conveyors had to be experimentally determined for each kind of dough, since there is no single formula that can be applied to all viscoelastic materials, which have widely varying properties.
Further, even with the same dough, an additional condition must be taken into account for the determination of the feed speed of the intermediate conveyor when the stretching rate is changed. Thus, an apparatus of this kind has been manufactured on the basis of data almost comparable to a data table of random numbers, leading to a very complex clutch mechanism for the apparatus.